课后答案 专业英语翻译

1. Metals and Their Use

It is known that metals are very important in our life. Metals have the greatest importance for industry. All machines and other engineering constructions have metal parts; some of them consist only of metal parts.

There are two large groups of metals:

1) Simple metal- more or less pure chemical elements

2) Alloys - materials consisting of a simple metal combined with some other elements.

About two thirds of all elements found in the earth are metals, but not all metals may be used in industry. Those metals which are used in industry are called engineering metals. The most important engineering metal is iron , which in the form of alloys with carbon and other elements, finds greater use than any other metal. Metals consisting of iron combined with some other elements are known as ferrous metals; all the other metals are called nonferrous metals. The most important nonferrous metal are copper , aluminum , lead , zinc , tin , but all these metals are used much less than ferrous metals, because the ferrous metals are much cheaper.

Engineering metals are used in industry in the form of alloys because the properties of alloys are much better than the properties of pure metals. Only aluminum may be largely used in the form of simple metal. Metals have such a great importance because of their useful properties or their strength, hardness, and their plasticity .

Different metals are produced in different ways, but almost all the metal are found in the forms of metal ore (iron ore, copper ore, etcet cetra.)

The ore is a mineral consistence of a metal combined with some impurities . In order to produce a metal from some metal ore, we must separate these impurities from the metal that is done by metallurgy .

2. Plastics and Other Materials

Plastics have specific properties which may make them preferable to traditional materials for certain uses. In comparison with metals, for example, plastics have both advantages and disadvantages. Metals tend to be corroded by inorganic acids , such as sulphuric acid and hydrochloric acid. Plastics tend to be resistant to these acids, but can have dissolved or deformed by solvent , such as carbon tetrachloride , which have the same carbon base as the plastics. Color must be applied to the surface of metals, whereas it can be mixed in with plastics. Metals are more rigid than most plastics while plastics are very light, with a specific gravity normally between 0.9 and 1.8. Most plastics do not readily conduct heat or electricity . Plastics soften slowly and can easily be shaped when they are soft.

塑料具有特殊的性能。对于某种用途而言，这些性能使得塑料比传统材料更为可取。例如，跟金属相比较，塑料既有优点也有缺点。金属易受到无机酸的腐蚀，如硫酸和盐酸，塑料能抵抗这些酸的腐蚀，但可被溶剂所洛解或引起变形，例如溶剂四氯化碳与塑料具有同样的碳基。颜色必定只能涂到金属的表面。而它可以跟塑料混合为一体。金属比大多数塑料刚性要好，而塑料则非常之轻，通常塑料密度在0. 9-1. 8之间。大多数塑料不易传热导电。塑料能缓慢软化，而当其还是在软的状态时，能容易成形。

It is their plasticity at certain temperatures which gives plastics their main advantages over many other materials. It permits the large-scale production of molded articles, such as containers, at an economic unit cost, where other materials require laborious and often costly processes involving cutting, shaping, machining, assembly and decoration.

在某一温度下塑料是处于塑性状态的，这就使塑料具备超过许多其他材料的主要优点。它容许大量生产单位成本低廉的模制式器件，例如，各种容器。于此，若用其他材料则需要大量劳力和往往需要很

费钱的加工工艺，比如，切割、成形、加工、装配和装饰。

Plastics not only replace other materials. Their properties can be exploited for entirely new applications. For example, plastics heart valves and other human 'spare parts' have make possible many recent developments in surgery .

There is no single plastics material which is suitable for all applications. It is important that the most suitable plastics should be chosen, and if necessary adapted, for each particular requirement. It is also important that the properties of the plastics chosen should be exploited to the best advantage.

A plastics article may need to differ in design and appearance from a similar article made from another material such as metal or wood. This is due not only to the properties of plastics but also to the techniques employed in fabricating plastics. These techniques include injection molding , blow molding, compression molding, extrusion and vacuum forming.

3. Casting and Die-Casting Alloys

Casting is one of the oldest metal working techniques known to man. Our country made metal castings as early as 2000 B.C., and the process used then is not much different in principle from the one used today.

铸造是入类所掌握的最古老的金属加工技术之一。我国早在公元前2000年就已把金属制成铸件，而所使用的工艺从原理上和今天的工艺没有多大的区别。

Foundry processes consist of making molds, preparing and melting the metal, pouring the metal into the molds, and cleaning the castings. The product of the foundry is a casting, which may vary from a fraction of a kilogram to several hundred tons. It may also vary in composition as practically all metals and alloys can be cast.

铸造工艺由制模、备料和金属熔炼，金属液浇注入模和铸件清砂等。铸造的产品是铸件，铸件可能从零点几公斤到几百吨范围变化。实际上所有金属在成分上也是变化的，而合金也可以铸造。

The metals most frequently cast are iron, steel, aluminum and so on. Of these, iron, because of its low melting point, low price and ease of control, is outstanding for its suitability ? for casting and is used far more than all the others.

最常铸造的金属是铸铁、钢、铝等等。这些金属中，铸铁，由于其低熔点，低价格和易控制，因而其铸造适应性是最突出的，而且使用也远比所有其他金属多。

Casting is a widely used method of producing metal products, particularly those which are intricate . Since molten materials will readily take the shape of the container into which they are poured, it is nearly as easy to cast fairly complex shapes as to produce simple forms.

由于熔融的物料能容易取得被浇注进去的容器〔模型)的形状，因此，几乎像生产简单形状铸件那样颇为容易地铸造出复杂形状的铸件。

The place where the metals are cast is called a foundry. The most important of cast metals is cast iron which is made from pig iron by remelting it in a special melting furnace called a cupola .

铸造金属的地方叫做铸造车间。最重要的铸造金属是铸铁，铸铁是用生铁在一个特殊的熔炉—叫冲天炉的炉子中重新熔炼而制造出来的。

From the cupola, the cast iron flows into ladles of different size, and from these ladles it is poured into the molds.

从冲天炉中出来的铁水流入到不同规格的铁水包中，并从这些铁水包中被浇注到模型中。

The molds may be of two kinds: sand molds and metal molds. A metal mold consists of two hollow parts which should be joined for pouring the metal into it. The inside of this mold is covered with carbon or graphite so that the metal could not stick to the wall of the form. When the metal has solidified , these hollow parts are disjoined and the casting is taken out. There are also special

molds in which large blocks of steel can be cast. These molds are usually made of cast iron and are called ingot molds, which the blocks of steel produced by pouring the metal into these molds are called ingots and the process is called ingot casting.

模型有两种类型:砂模和金属模。金属模是由两个中空的部件组成，它们应被联结在一起以便将金属液浇入模箱中。这模腔的内侧是要涂以碳粉或石墨，因此金属不玫于粘贴到型腔壁上口当金属液凝固后，这中空的型箱部件被打开并取出铸件。也有一种特殊模型，在该模型中可以铸造大型钢块。这些模型通常用铸铁米制造，并被称为锭模。而浇注金属液到这些模子中生产出的钢块被称为钢锭。该工艺过程叫锭铸。

A relatively wide range of nonferrous alloys can be die-cast. The principal base metals used, in order to commercial importance, are zinc, aluminum, copper, magnesium , lead, and tin. The alloys may be further classified as low-temperature alloys and high-temperature alloys; those having a casting temperature below 538C, such as zinc, tin, and lead, are in the low-temperature class. The low-temperature alloys have the advantages of lower cost of production and lower die-maintenance costs. As the casting temperature increases, alloy and other special steels in the best treated condition are required to resist the erosion and heat checking of die surface. The destructive effect of high temperatures on the dies has been the principal factor in retarding the development of high-temperature die castings.

相当大量的有色金属合金可以进行模铸}h用的主要而基本的金属，按其在工业上应用的重要性的顺序是锌、铝、铜、锰、铅和锡。这些合金可以进一步进行分类为低温类合金和高温类合金。铸造温度低于538℃的那些合金，就像锌、锡和铅,是属于低温类合金。低温类合金具有低生产成本和低的模具维修费用等优点。当铸造温度上升时，需要最佳条件下处理过的合金钢和其他特种钢来抵抗腐蚀及防止模具表面的热裂纹。高温在模具上的损坏作用已经成为阻碍、延缓高温模铸发展的主要因素。

Another factor governing the choice of alloy is the erosive or solvent action of the molten metal on the respective machine parts and dies. This action increases with temperature, although it is more pronounced with some alloys than with others. Aluminum, in particular, has a destructive action on ferrous metals and, for this reason, is seldom melted in the machine, whereas the copper-base alloys are never melted in the machine.

控制选择合金的另外一个因素就是熔融的金属在相关的机器零件上和模具上的腐蚀或溶解作用。这种作用随着温度的升高而增加，甚至某些合金比另一些合金更为明显。特别是.铝对黑色金属有一种破坏作用，为此、铝几乎不熔混于机器零件中，而铜基合金是决不能熔混于机器构件中的。

4. Forging

Press forging employs a slow squeezing action in deforming the plastic metal, as contrasted with the rapid-impact blows of a hammer. The squeezing action is carried completely to the center of the part being pressed, thoroughly working the entire section . These presses are the vertical type and may be either mechanically or hydraulically operated. The mechanical presses, which are faster operating and most commonly used, range in capacity from 500 to 1000 tons.

与锤锻的快速冲击不同，压力机锻造是用缓慢的挤压作用使塑性金属变形。这挤压作用完全被施加到正在被压锻的零件中心位置上，直至彻底使整个工件得到加工。这些压力机都是立式的，可能是机械操作也可能是液压操作的。机械操作压力机，操作速度比较快，使用最普遍，锻造能力从5400吨到10000吨范围。

For small press forgings, closed impression dies are used and only one stoke of the ram is normally required to perform the forging operation. The maximum pressure is built up at the end of the stroke which forces the metal into shape. Dies may be mounted as separate units, or all the cavities may be put into single block. For small forgings, individual die unites are more convenient. There is some difference in the design of dies for different metals; copper-alloy forgings can be made with less draft than steel,

consequently more complicated shapes can be produced. These alloys flow well in the die and are rapidly extruded

对于小型压力锻使用闭式锻模。通常要求锻锤仅一个冲程就完成锻造工艺。在冲程终端产生最大压力，该冲击压力迫使金属成形。模具可由各白独立的单元装配而成，即把所有个别模腔都放到一起，组成整体。对于小型锻件使用分模装置更为方便。对于不同的金属在模具设计上有些区别.铜合金锻件比钢件用较小的拔模斜度，因此可生产更加复杂形状的锻件。这些合金在该种模具中流动性好，而且能快速挤压成形。

In the forging press, a greater proportion of the total work put into the machine is transmitted to the metal than in a drop hammer press. Much of the impact of the drop hammer is absorbed by the machine and foundation. Press reduction of the metal is faster, and the cost of operation is consequently lower. Most press forgings are symmetrical in shape, having surfaces which are quite smooth, and provide a closer tolerance than is obtained by a drop hammer. However, many parts of irregular and complicated shapes can be forged more economically by drop forging. Forging press is often used for sizing operations on parts made by other forging processes.

锻压机比落锤锻，输入到机器里的总能量中有更大部分的能量被传输到金属坯料上。落锤锻的冲击能量被机器和基础吸收得较多(比起压力机来〕。金属上的压力衰减较快，因此生产成本比较低。大多数压力锻锻件形状、产生的表面都是对称的，而且表面非常光滑，并比落锤锻件的公差尺寸更加精确。然而落锤锻造可以锻制形状复杂而不规则的锻件，因而较为经济。锻压机常常用来为其他锻造工艺所生产的锻件进行整形和校正加工用。

In drop forging, a piece of metal, roughly or approximately of the desired shape, is placed between die faces having the exact form of the finished piece, and forced to take thin form by drawing the dies together. Large ingots are now almost always forged with hydraulic presses instead of with steam hammers, since the work done by a press goes deeper. Further, the press can take a cooler ingot and can work to closer dimensions . The forging should be done at about the same temperature as rolling ; the process improves the physical properties of the steel just as rolling does. In the final forging it is important not to have the steel too hot, for overheated steel will have poor mechanical properties when cooled. In heating for forging, temperature is usually judges by the eye, but where large numbers of the same pattern are made, the piece to be forged are heated in furnaces in which the temperature is indicated by pyrometers , and often is automatically controlled.

在落锤锻中，一块金属坯料，粗糙的即大体像所要求零件形状那样，被放入到具有成品件那样精确形状的模面之间，然后施加压力使模具紧紧结合在一起以锻取模腔形状。这一方法广泛用来制造钢件和黄钢件。大型金属锭现在几乎都是用液压压力机来锻造的，而不用蒸汽锤。因为用压力机锻造，变形更加深透。将来压力机可对付冷金属锭并能加工得到更加精确的尺寸。锻造将在大约与辊轧同样的温度下进行，这种工艺正像轧制那样可改善金属的物理性能。最后火锻时，不使钢太热很重要，因为过热钢冷却后，其机械性能较差。为锻件加热，温度通常是以肉眼来判断的，但在生产大量相同锻件的场合，要锻造的坯件是在有高温计指示温度的炉子中来加热，并且常常是自动控制的。

5. Soldering and Welding

There are a number of methods of joining metal articles together, depending on the type of metal and the strength of the joint which is required.

把金属件连接在一起的方法有若干个，用哪一种方法，要根据金属种类和所要求的焊缝强度来决定。

Soldering is the process of joining two metals by a third metal to be applied in the molten state. Solder consists of tin and lead, while bismuth and cadmium are often included to lower the melting point. One of the most important operations in soldering is that of cleaning the surface to be joint, this may be done by some acid cleaner.

软焊是要用溶融状态的第三种金属来使两件金属连接在一起的工艺。焊料由锡和铅组成。而常常含

有铋和镉。目的是要降低熔点。软钎焊中最重要的工序之一就是清理焊缝表面。这可以用某种酸性清除剂来进行。

Soldering gives a satisfactory joint for light articles of steel, copper or brass , but the strength of a soldered joint is rather less than a joint which is brazed , riveted or welded . These methods of joining metal are normally adopted for strong permanent joints.

软钎焊能为轻型钢件、铜件和黄铜件生产满意的焊缝，但软钎焊的焊缝强度比起硬钎焊、铆接和焊接来要弱些。连接金属的这些方法，通常用来产生强固的永久性的焊缝。

The simplest method of welding two pieces of metal together is known as pressure welding. The ends of metal are heated to a white heat-for iron, the welding temperature should about 1300C-in a flame . At this temperature the metal becomes plastic. The ends are then pressed or hammered together, and the joint is smoothed off. Care must be taken to ensure that the surfaces are thoroughly clean first, for dirt will weaken the weld. Moreover, the heating of iron or steel to a high temperature causes oxidation , and a film of oxide is formed on the heated surfaces. For this reason, a flux is applied to the heated metal. At welding heat, the flux melts, and the oxide particles are dissolved in it together with any other impurities which may be present. The metal surfaces are pressed together, and the flux is squeezed out from the center of the weld. A number of different types of weld may be used, but for fairly thick bars of metal, a v-shaped weld should normally be employed . It is rather stronger than the ordinary but weld.

把两件金属焊在一起的最简单的方法称做压力焊。用火焰把金属两端加热到白炽状态—铁的焊接温度为1300C左右—在这一温度下，金属变成塑性，然后对两端施压或锤击使之结合在一起。最后再将焊缝清理千净。必须注意首先保证表面完全清洁，因脏物将会使焊缝强度削弱。此外，加热铸铁或钢到高温会引起氧化井在焊接表面形成氧化皮。因此用助焊剂施于加热的金属上。达到焊接温度时刻，助焊剂熔化，将氧化物粒子跟任何其他可能存在的杂质一起都熔解于助焊剂中，金属表面被压合在一起，而助焊剂就从焊缝中间被挤出。可能使用若干不同类型的焊缝，但对于颇为粗厚的金属件，通常使用V 型焊缝。该焊缝比起普通的对接焊缝来要强固些。

The heat for fusion welding is generated in several ways, depending on the sort of metal which is being welded and on its shape. An extremely hot flame can be produced from an oxy-acetylene torch. For certain welds an electric arc is used. In this method, an electric current is passed across two electrodes , and the metal surfaces are placed between them. The electrodes are sometimes made of carbon, but more frequently they are metallic . The work itself constitutes one of them and the other is an insulated filler rod. An arc struck between the two, and the heat which is generated melts the metal at the weld. A different method is usually employed for welding sheets or plates of metal together. This is known as spot welding. Two sheets or plates are placed together with a slight overlap, and a current is passed between the electrodes. At welding temperature, a strong pressure is applied to the metal sheets. The oxide film, and any impurities which are trapped between the sheets, are squeezed out, and the weld is made.

可用几种方法来产生溶焊的热，用何种方法，要根据将要焊接的金属种类和根据其形状来决定。由氧乙炔焰可产生强烈的火焰。对于某种焊缝，可用电弧来焊接。在这一系列重要的焊接过程中，电弧可为熔化金属供热，而焊剂起着保护和清理焊缝的作用，而且常常也是起着熔炼控制作用。最广泛使用的助焊剂保护电弧焊的形式是一种称作金属弧焊的手工操作工艺。在这一方法中，电流经两个电极流过，而金属表面则被置于两电极之间。电极(电焊条)有时用碳棒制作，但更常用金属来制作。工件本身构成它们中的一极而另一极是一具有绝缘填充剂的焊条。两极之间电弧放电，由此产生的热去熔化在焊缝处的金属。通常使用不同的方法去把金属薄板或厚板焊接在一起。这就叫做点焊。两块薄板或厚板以边沿稍稍搭叠的方式放在一起，一电流从两极之间通过.达到焊接温度时刻，对金属板施加强压，氧化皮和陷入薄板中间任何杂质都会被挤出，而完成了焊缝连接.

6. Heat Treatment and Hot Working of Metals

We can alter the characteristics of steel in various ways. In the first place, steel which contains very little carbon will be milder than steel which contains a higher percentage of carbon, up to the limit of about 1.5%. Secondly, we can heat the steel above a certain critical temperature, and then allow it to cool at different rates. At this critical temperature, changes begin to take place in the molecular structure of the metal. In the process known as annealing , we heat the steel above the critical temperature and permit it to cool very slowly. This causes the metal to become softer than before, and much easier to machine. Annealing has a second advantage; it helps to relieve any internal stresses which exist in the metal. These stresses are liable to occur through hammering or working the metal, or thorough rapid cooling. Metal which we cause to cool rapidly contracts more rapidly on the outside than on the inside. This produces unequal contractions, which may give rise to distortion or cracking . Metal which cools slowly is less liable to have these internal stresses than metal which cools quickly.

On the other hand, we can make steel harder by rapid cooling. We heat it up beyond the critical temperature, and then quench it in water or some other liquid. The rapid temperature drop fixes the structure change in the steel which occurred at the critical temperature, and makes it very hard. But a bar of this hardened steel is more liable to fracture than normal steel. We therefore heat it again to a temperature below the critical temperature, and cool it slowly. This treatment is called tempering . It helps to relieve the internal stresses, and makes the steel less brittle than before. The properties of tempered steel enable us to use it in the manufacture of tools which need fairly hard steel. High carbon steel is harder than tempered steel, but it is more difficult to work.

These heat treatments take place during the various shaping operations. We can obtain bars and sheets of steel by rolling the metal through huge rolls in a rolling mill . The roll pressures must be much greater for cold rolling than for hot rolling, but cold rolling enables the operators to produce rolls of great accuracy and uniformity , and with a better surface finish. Other shaping operations include drawing into wire, casting in moulds, and forging.

The mechanical working of metal is the shaping of metal in either a cold or hot state by some mechanical means. This does not include the shaping of metals by machine or grinding, in which processes metal is actually machined off, not does it include the casting of molten metal into some form by use of molds. In mechanical working processes, the metal is shaped by pressure-actually forging, bending , squeezing, drawing, or shearing it to its final shape. In these processes the metal may be either cold-or hot- worked. Although normal room temperatures are ordinarily used for cold working of steel, temperatures up to the recrystallization range are sometimes used. Hot working of metals takes place above the recrystallization or work-hardening range. For steel, recrystallization starts around 650 to 700C, although most hot work on steel is done at temperature considerably above this range. There is no tendency for hardening by mechanical work until the lower limit of the recrystalline range is reached. Some metals, such as lead and tin, have a low recrystalline range and can be hot-worked at room temperature, but most commercial metal require some heating. Alloy composition has a great influence upon the proper working range, the usual result being to raise the recrystalling range temperature. This range may also be increased by prior cold working.

7. Kinds of Steels, Mechanical Properties of Metals

There are two general kinds of steel: carbon steel and alloy steel. Carbon steel contains only iron and carbon, while alloy steel contains some other alloying elements such as nickel , chromium , manganese , molybdenum , tungsten , vanadium , etc.

1. Carbon steels

(1) Low carbon steel containing from 0.05 to 0.15 percent carbon; this steel is also known as machine steel.

(2) Medium carbon steel containing from 0.15 to 0.60 percent carbon.

(3) High carbon steel containing from 0.6 to 1.50 percent carbon: this steel is sometimes called "tool steel".

2. Alloy steels

(1) Special alloy steel, such as nickel steel, chromium steel.

(2) High-speed steel also known as self-hardening steel.

Carbon steels are the most common steels used in industry. The properties of these steels depend on the percentage of carbon they contain. Low-carbon steels are very soft and can be used for bolts and for machine parts that do not need strength.

Medium carbon steel is a better grade and stronger than low carbon steel. It is also more difficult to cut than low carbon steel.

High carbon steel may be hardened by heating it to a certain temperature and then quickly cooling in water. The more carbon the steel contains and the quicker the cooling is, the harder it becomes. Because of its high strength and hardness, this grade of steel may be used for tools and working parts of machines.

But for some special uses, for example, for gears , bearings , springs , shafts and wire , carbon steels cannot be always used because they have no-properties needed for these parts.

Mechanical properties are the characteristic responses of a material to applied forces. The knowledge of mechanical properties of materials is very essential in order to construct a mechanically sound structure such as a bridge on the river. Mechanical properties can be determined by conducting experimental tests on the material specimen . Some important mechanical properties of materials are:

(1) Strength (in tension, compression, shear and bending)

(2) Stiffness

(3) Ductility

(4) Impact strength

(5) Hardness

(6) Toughness

1. Strength or mechanical strength of a material may be defined as the ability of the material to sustain loads without undue distortion or failure. Material should have adequate strength when subjected to tension, compression, shear, bending or torsion as per the intended use.

For example the crankshaft of an automobile should have proper torsion strength.

2. Stiffness. Stiffness is the ability of a material or shape to resist elastic deflection . For identical shapes, the stiffness is proportional to the modulus of elasticity . A material which deforms less under a given load is more stiff than on which deforms more.

8. Gears and Reducers

Gears are vital factors in machinery . One of the first mechanism invented using gears was the clocks. In fact, a clock is little more than a train of gears. Considerable study and research have been made on gears in recent years because of their wide use under exacting conditions. They have to transmit heavier loads and run at higher speeds than ever before. The engineers and the machinists all consider gearing the prime element in nearly all classes of machinery.

1. Spur gears

Spur gears are used to transmit power and rotary motion between parallel shafts. The teeth are cut parallel to the axis of the shaft on which the gears are mounted. The smaller of two gears in mesh is called the

pinion , and the larger is customarily ?? designated as the gear. In most applications, the pinion is the driving element whereas the gear is the driven element.

2. Helical gears

Helical gears have certain advantages, for example, when connecting parallel shafts they have a higher load-carrying capacity than spur gear with the same tooth numbers and cut with the same cutter.

Helical gears can also be used to connect nonparallel , non-intersecting shafts at any angle to one another.

The maximum gear ratio obtainable with a single pair of gears varies with the type of gear and the application. The following are approximate maxima for the various type for average load conditions: spur, 8; parallel-shaft helical, 10; straight bevel , 6; spiral bevel, 8; hypoid , 12; and worm , 80. For lightly loaded, instrument , and positioning gears, these rations can be exceeded . Rations as high as 400 or higher can be obtained with gears that resemble tapered worms meshing with hypoid gear. For heavily loaded gear, the given rations may be so high that a reasonable gear size precludes a satisfactory pinion.

Since the ratio in a single pair of gears is the quotient of the tooth number, and since there usually are limitations on both the minimum and maximum numbers of teeth on the available gears, it follows that the number of ratios obtainable in a single pair is limited. To enlarge the coverage it is necessary to use multiple pairs, or trains. The overall speed ratio in a train is the product of the ratios in each pair. In certain cases an exact ratio cannot be obtained with gears, but by using two or more parts, the desired ratio can be approximated to any degree of precision.

As a convenience for machine builders and users, packaged speed reducers, following an industry-accepted pattern , are manufactured in a wide variety of types, configurations , speed ratios, and capacities; these consist of a box or housing containing bearings, shafts, lubricant , and shaft oil seals . Speed increasers are usually custom build.

All speed reducers when operating continuously become hot because of friction in the teeth, in the lubricant, in the bearings, and in the oil seals. If the heat is generated at a faster rate than it can be dissipated to the atmosphere, the lubricant may deteriorate and the gear or bearing fail.

9. Worm Gear Sets

Worm gear sets are widely used because of the many advantages obtained by their tooth action and load carrying capacity . A large speed reduction or a high increase of torque can be attained with the worm gear set. Compactness of design is easy to obtain with such a combination . Worm gear drives are quiet and vibration free.

A worm gear set consists of the worm, which is very similar to a screw , and the worm gear, which is a helical gear. The shafts upon which the worm and the gear are mounted are usually at right angels but not in the same plane . The usual practice is to have the worm drive the worm gear. With same ratios , it is possible to have a gear driver the worm. However, with large ratios, it is impossible for the gear to drive the worm.

The worm can be made with either right-hand or left-hand thread. Also, like a screw, it can be made with single, double, triple , or quadruple thread. A single-thread worm advances the worm gear a distance equal to pitch for each complete worm rotation. The distance advanced is called the lead . Thus, the pitch equals the lead for a single thread. A double-threaded worm has a lead which is twice the pitch.

The geometry of a worm is similar to that of a power screw. Rotation of the worm simulates a linearly advancing involute rack . The geometry of worm gear (sometimes

called a worm wheel ) is similar to that of a helical gear, except that the teeth are curved to envelop the worm. Sometimes the worm is modified to envelop the gear. This gives a greater area of contact, but requires extremely precise mounting.

10. Cams

A rotary cam is part on a machine which mechanically changes cylindrical motion to straight-line motion. The cam, which is mounted on a shaft, is usually driven by a motor either applied directly to the cam shaft or connected by pulleys or gears. The purpose of a cam is to transmit various kinds of motions to other parts of a machine.

Practically every cam must be designed and manufactured to fit special requirements. Though each cam appears to be quite different from the other, all the cams work in a similar ways. In each case, as the cam is rotated or turned, another part in contact with the cam, called a follower, is moved either left and right, up and down, or in and out. The follower is usually connected to other parts on the machine to accomplish the desired action. The direction the follower move depends upon the position of the framework which attaches the cam and follower to the machine. If the follower loses contact with the cam, it will fail to work.

The faster the cam turns, the more rapid is the motion of the follower. The motion of the follower caused by rotating the cam is exactly the same for each complete turn of the cam.

11. Belt drives

Belt drives offer a maximum of versatility ? as power transmission elements. They allow the designer considerable flexibility in location of driver and driven machinery, and tolerances are not critical as is the case with gear drives. Another advantage of belt drives is that they reduce vibration and shock transmission. Furthermore, belt drives are relatively quiet.

Large flat leather belts were in general use many years ago, when the usual practice was to use one large engine to driver several different pieces of machinery. Some leather belts are in use at this time as well as flat steel, rubber, plastic, and fabric belts. Light, thin flat belts are practical on high speed machinery where vibration may be a problem

V belts are probably the most common means of transmitting power between electric motor and driven machinery. Conventional V belts are made of rubber. Most often, both driver and driven pulleys lie in the same vertical plane, and the speed ration is constant .

Smooth flat belt and V belts depend on friction on the pulleys and some slippage is inherent in their operation. Therefore, speed ratios are not precise . Most heavy duty pulleys are made of cast iron or formed steel.

Note that the capacity of the belt drive is determined by the angle of wrap on the smaller pulley, and that this is particularly critical for drives involving pullets of greatly differing size, special closely together.

12. Keys and Springs

Keys are used to prevent relative motion between a shaft and machine elements such as gears, pulleys, sprockets , cams, levers , flywheels , impellers , and so on. There are numerous kinds of key (some of which have been standardized ) for various design requirement. The keys most frequently used are the square key, the tapered key, and the woodruff key.

Perhaps the most common of these torque-transmitting shaft-to-hub connections are keys, of which the

most common type is the square key. Standard proportions call for the key width to be approximately one-forth the shaft diameter . Keys are usually made of cold-finished low-carbon steel, but heat-treated alloy steels are used when greater strength is required.

Mechanical springs are used in machines to exert force, to provide flexibility and to store or to absorb energy. In general, springs may be classified as either wire springs or flat springs, although there are variation within these divisions. Wire springs include helical springs of round, square, or special-section wire and are made to resist tensile , compressure or torsional loads. Under flat springs are included the cantilever and elliptical types, the clocktype power-springs and the flat spring washers , usually called Belleville springs.

In one word, springs are elastic members that exert forces (or torques) and absorb energy (which is usually stored and later released ). Springs are usually, but not necessarily, made of metal. Plastics can be used when loads are light.

13. Screw

Screws have been used as fasteners for a long time. As indicated in the section on single machine, a screw acts with a wedging action and consists of a circular cylinder (or truncated cone ) with a helical groove in it. When used for fastening, all screws are provided with means for applying a torque (twisting moment) to them; this may consist of a square of hexagonal head for a wrench, a head with a slot or a cross-shaped recess for a screwdriver , a cylindrical head with a recess fitting a special wrench, or a slot or recess on one end fitting a screwdriver or special wrench and no head.

Screws with screwdriver slots have heads of several shapes, such as flat, oval, round, and fillister (cylindrical with a round top). Wood screws are tapered , and self-tapping screws have tapered ends and a variety of special points. The latter are usually hardened and cut or form a mating internal thread when screwed into the proper size hole.

Screws with hexagonal heads are usually known as cap screws. Screws with other types of heads are also known as cap screws in the larger sizes and as machine screws in the small sizes. All of these screws are used to clamp machine parts together when one of the parts has an internal thread. If neither part is threaded a bolt must be used: this consist of screw with a hexagonal head, a nut (hexagonal ring with an internal thread), and usually a washer (flat ring). A stud has threads on both ends and no means for turning. It is permanently screwed into one member and clamps by means of a nut on the other end. All of these fasteners stretch when tightened, and the tensile load created in this way clamps the members together.

Set screws differ in form and function from the other type of screws. They are hardened and have cup, cone, oval, flat, and dog (cylindrical) ends or points. They are usually headless and are frequently used as substitutes for keys or in conjunction with keys in shaft-mounted members. The set screw fits in a threaded radial hole in the hub, and the point is tightened down into a hole, a flat, or a dimple in the shaft or key. Set screws are stressed in compression and in action they create a helical wedge between the connected pates.

14. Shafts

As a machine component , a shaft is commonly a cylindrical bar that supports and rotates with devices for receiving and delivering rotary motion and torque. The crankshaft of a reciprocating engine receives its rotary motion from each of the cranks , via the pistons and connecting rod (the slider-crank mechanisms ), and delivers it by means of couplings , gears, chains , or belts to the transmission, camshaft, pumps, and other devices. The camshaft , driven by a gear or chain from the crankshaft, has only one receiver or input, but each cam on the shaft delivers rotary motion to

the valve-actuating mechanisms.

An axle is usually defined as a stationary cylindrical member on which wheels and pulleys can rotate, but the rotating shaft that drive the rear wheels of an automobile are also called axles, no doubt a carryover from horse-and-buggy^i days. It is common practice to speak of short shafts on machines as spindles , especially tool-carrying or work-carrying shafts on machine-tool.

In operation, shafts are subjected to a shearing stress, whose magnitude depends on the torque and the dimensions of the cross section. This stress is a measure of the resistance that the shaft material offers to the applied torque. All shafts that transmit a torque are subjected to torsional shearing stress, In addition to the shearing stresses, twisted shafts are also subjected to shearing distortions . The distorted state is usually defined by the angle of twist per unit length, i.e., the rotation of one cross section of a shaft relative to another cross section at a unit distance from it.

15. Bearings

A bearing is a connector that permits the connected members to either rotate or translate (move to and fro) relative to one another but prevent them from separating in the direction in which loads are applied. In many cases one of the members is fixed, and the bearing acts as a support for the moving member.

The relative motion in bearings is always opposed by friction, and the work done in overcoming friction is lost power in all machines. Consequently ? , much thought and effort have been devoted to the development of bearings with minimum friction. In all bearings there are two surfaces (one belonging to each of the connected parts) that move relative to one another. To minimize friction, the co-acting surfaces may be partially or completely separated by a film of liquid or gas; these are known as sliding-contact bearings. The surfaces may be separated also by an assemblage of rolling elements such as balls and rollers; these are known as roll-contact bearing.

Sliding bearings are the simplest to construct and, considering the multitude of pin-jointed devices and structures in use, are probably the most commonly used.

The essential parts of a ball bearing- the inner and outer ring, the balls, and the separator-are shown in figure . The inner ring is mounted on a shaft and has a groove in which the balls ride. The outer ring is usually the stationary part of the bearing and also contains a groove to guide and support the balls. The separator prevents contact between the balls and thus reduces friction, wear , and noise from the regions where severe sliding conditions would occur. In a few applications where operating conditions are mild, the rings and separator can be omitted and loose balls interposed between the shaft and housing . This type of bearing is sometimes found in bicycles. The vast majority of ball bearings, however, are preassembled units consisting of four elements. There are many types of bearings because of variations in the design of rings and separators and in the number of balls. They can be divided into classes according to their function: those that support a combination of a radial load, those that support a thrust load, or those that support a combination of thrust and radial loads. The last type is termed "angular-contact bearing."

In deep-groove ball bearings, the races are approximately one fourth as deep as the ball diameter . A cross section of the ball and outer ring of a deep-groove ball bearing is shown in figure. Although deep-groove ball gearings are designed to carry a radial load, they perform well under a combined radial and thrust load. For this reason, this is the most widely used type of ball bearing.

16. Couplings

A coupling is a device for connecting the ends of adjacent shafts. In machine construction, couplings are used to effect a semipermanent ?? connection between adjacent rotating shafts. The connection is permanent in the sense that it is not meant to be broken during the useful life of the machine, but it can be broken and restored in an emergency or when worn parts are replaced.

There are several types of shaft couplings; their characteristics depend on the purpose for which they are used. If an exceptionally long shaft is required for a line shaft in a manufacturing plant or a propeller shaft on a ship, it is made in sections that are coupled together with rigid couplings.

A common type of rigid coupling consists of two mating radial flanges (disks) that are attached by key-driven hubs to the ends of adjacent shaft sections and bolted together through the flanges to form a rigid connection. Alignment of the connected shafts is usually effected by means of a rabbet joint on the face of the flanges, i.e., a short cylindrical projection on the face of one flange fits snugly in a circular recess on the face of the other flange.

In connecting shafts belonging to separate devices (such as an electric motor and a gear-box), precise aligning of the shafts is difficult and a flexible coupling is used. This coupling connects the shafts in such a way as to minimize the harmful effects of shaft misalignment . Flexible couplings also permit the shafts to deflect under their separate systems of loads and to move freely (float) in the axial direction without interfering with one another. Flexible couplings can also serve to reduce the intensity of shock loads and vibrations transmitted from one shaft to another.

The flexibility provided by a coupling may be only spatial , or it may be both spatial and resilient (springy ); in other words the coupling may compensate for shaft misalignment but provide no resilience, or it may be resilient and provide also for a small amount of misalignment.

17. Clutches

A clutch is a device for quickly and easily connecting or disconnecting a rotatable shaft and a rotating coaxial shaft. Clutches are usually placed between the input shaft to a machine and the output shaft from the driving motor, and provide a convenient means for starting and stopping the machine and permitting the driver motor or engine to be started in an unloaded state.

The rotor (rotating member) in an electric motor has rotational inertia , and a torque is required to bring it up to speed when the motor is started. If the motor shaft is rigidly connected to a load with a large rotational inertia, and the motor is started suddenly by closing a switch , the motor may not have sufficient torque capacity to bring the motor shaft up to speed before the windings in motor are burned out by the excessive current demands. A clutch between the motor and the load shafts will restrict the starting torque on the motor to that required to accelerate the rotor and parts of the clutch only.

On some machine tools, it is convenient to let the driving motor run continuously and to start and stop the machine by operating a clutch. Other machine tools receive the power from belts driven by pulleys on intermediate shafts that are themselves driven by belts from long lineshafts that serve a group of machine. Two pulleys that can be connected to the intermediate shaft by clutches, and driven in opposite directions by open and crossed belts from the line shaft, can provide forward and reverse rotation for the machine.

18. Brakes

Basically, brakes are devices for controlling the flow of motion in machine, and in this respect they resemble clutches; clutches start the flow while brakes arrest it. Before the engagement of a clutch or a brake, one of the two members in the device is moving while the other is stationary; after the engagement of a clutch both members are moving at the same speed, while after the application of a brake the moving member is either slowed down or stationary . In both cases

the desired effects are produced by devices that are so alike, structurally , that they can sometimes serve in either capacity .

In arresting the motion of bodies, brakes must be capable of absorbing kinetic energy. Even when acting on translating bodies (like automobiles) most brakes are designed to act on rotating mechanical elements and to absorb energy either mechanically, hydraulically , or electrically . Mechanical brakes are the most common: they dissipate kinetic energy in the form of heat generated by mechanical friction between a rotating metallic element and a nonrotating friction element, when they are brought in contact by either mechanical, hydraulic, pneumatic , or electrical means. The material in the friction element may be organic , metallic , or ceramic . Organic materials with an asbestos ? bases are satisfactory for the majority of applications. When service requirements are severe, however, the heat generated may cause "fading " (a drop in braking effectiveness caused by a reduction in the coefficient of friction). In such cases, sintered metallic linings are preferred because of their high thermal conductivity and freedom from fading. By adding ceramic particles to sintered metallic linings, extremely hard and fade-resistant linings can be produced.

The rotating element in a mechanical brake is either a drum, a disk, or a series of disks. The nonrotating friction element in a drum brake may be either a band or a pair of shoes (blocks) that contract around the outside of the drum or a pair of shoes that expand against the inside of the drum. A disk brake may be similar to a plat clutch, with alternate rotating metallic and nonrotating friction elements, or it may be of the caliper type, with a single rotating disk and two opposed friction pads that squeeze the disk between them in a pinching action.

19. Linkages

A linkage may be defined as an assemblage of solid bodies, or links, in which each link is connected to at least two others by pinpin connections (hinges ) or sliding joints . To satisfy this definition , a linkage must form an endless, or closed, chain or a series of closed chains. It is obvious that a chain with many links will behave differently from one with few. This raises the vitally important question regarding the suitability ?of a given linkage for the transmission of motion in a machine. This suitability depends on the number of links and the number of joints .

Degrees of freedom. A three-bar linkage (containing three bars linked together) is obviously a rigid frame; no relative motion between the links is possible. To describe the relative positions of the links in a four-bar linkage it is necessary only to know the angle between any two of the links.

This linkage is said to have one degree of freedom. Two angles are required to specify the relative positions of the links in a five-bar linkage: it has two degrees of freedom.

Linkages with one degree of freedom have constrained motion; i.e., all points on all of the links have paths on the other links that are fixed and determinate . The paths are most easily obtained or visualized by assuming that the link on which the path are required is fixed, and then moving the other links in a manner compatible with the constraints.

20. Functions of Lubricants

Although a lubricant primary controls friction and wear, it can and ordinarily does perform numerous other functions, which vary with the application and usually are interrelated.

Friction control: The amount and character of the lubricant made available to sliding surface have a profound effect upon the friction that is encountered. For example, disregarding such related factors as heat and wear but considering friction alone between two oil film lubricated surfaces, the friction can be 200 times less than that between the same surfaces with no lubricant. Under fluid-film conditions, friction is

directly proportional to the viscosity of the fluid. Some lubricants, such as petroleum derivatives , are available in a great range of viscosities and thus can satisfy a broad spectrum of functional requirements. Under boundary lubrication conditions, the effect of viscosity on friction becomes less significant than the chemical nature of the lubricant. For instance, delicate instruments must not be lubricated with fluids that would attack and corrode the finer metal.

Wear control: Wear occurs on lubricated surfaces by abrasion , corrosion , and solid-to-solid contact . Proper lubricants will help combat each type. They reduce abrasive and solid-to-solid contact wear by providing a filmfilm that increases the distance between the sliding surfaces, thereby lessening the damage by abrasive contaminants and surface asperities .

Corrosion wear is generally caused by the products of oxidation of petroleum lubricants. Use of oxidation inhibitors reduces deterioration of petroleum lubricants, and the addition of corrosion preventives protects metal surfaces from any oxidation products that do form.

Temperature control: Lubricants assist in controlling temperature by reducing friction and carry off the heart that is generated . Effectiveness depends upon the amount of lubricant supplied, the ambient temperature, and the provision for external cooling. To a lesser extent, the type of lubricant also affects surface temperature.

Corrosion control: The role of a lubricant in controlling corrosion of the surfaces themselves is twofold. When machinery is idle, the lubricant acts as a preservative . When machinery is in use, the lubricant controls corrosion by coating lubricated parts with a protective film that may contain additives to neutralize corrosive materials. The ability of a lubricant to control corrosion is directly related to the thickness of the lubricant film remaining on the metal surfaces and the chemical composition of the lubricant. Additives that react with the sliding surfaces enhance the corrosion control of the lubricant.

21. The lathe

The lathe is one of the most useful and versatile machine in the workshop , and is capable of carrying out a wide variety of machining operations. The main components of the lathe are the headstock and tailstock` at opposite ends of a bed, and a tool-post between them which holds the cutting tool. The tool-post stands on a cross-slide which enables it to move sidewards across the saddle or carriage as well as along it depending on the kind of job it is doing. The ordinary center lathe can accommodate only one tool at a time on the tool-post, but a turret lathe is capable of holding five or more tools on the revolving turret. The lathe bed must be very solid to prevent the machine from bending or twisting under stress.

The headstock incorporates the driving and gear mechanism, and a spindle which holds the workpiece and causes it to rotate at a speed which depends largely on the diameter of the workpiece. A bar of large diameter should naturally rotate more slowly than a very thin bar; the cutting speed of the tool is what matters. Tapered center in the hollow nose of the spindle and of the tail-stock hold the work firmly between them. A feed-shaft from the headstock drives the tool-post along the saddle, either forwards or backwards, at a fixed and uniform speed. This enables the operator to make accurate cuts and to give the work a good finish. Gears between the spindle and the feed-shaft control the speed of rotation of the shaft, and therefore the forward or backward movement of the tool-post. The gear which the operator will select depends on the type of metal which he is cutting and the amount of metal he has to cut off. For a deep or roughing cut the forward movement of the tool should be less than for a finishing cut.

Centres are not suitable for every job on the lathe. The operator can replace them by various types of chucks , which hold the work between jaws, or by a front-plate, depending on the shape of the work and the particular cutting operation. He will use a chuck, for example, to hold a short piece of work, or work for drilling , boring or screw-cutting. A transverse movement of the tool-post across the saddle enables

the tool to cut across the face of the workpiece and give it a flat surface. For screw cutting, the operator engages the lead-screw, a long screwed shaft which runs a long in front of the bed and which rotates with the spindle. The lead-screw drives the tool-post forwards along the carriage at the correct speed, and this ensures that the threads on the screw are of exactly the right pitch. The operator can select different gear speeds, and this will alter the ratio of spindle and lead-screw speeds and therefore alter the pitch of threads. A reversing lever on the headstock enables him to reverse the movement of the carriage and so bring the tool back to its original position.

22. Milling, Shaper, Planer and Grinding Machines

Milling machines

The milling machine is a machine that removes metal from work with a revolving milling cutter as the work in fed against it.

The milling cutter is mounted on an arbor where it is held in place by spacers or bushing . The arbor is fixed in the spindle with one end, while the other end of the arbor rotates in the bearing mounted on the arbor yoke .

The most important parts of the milling machine are: 1) starting levers ; 2) spindle; 3) column; 4) knee; 5) elevating screw; 6) table; 7) index head; 8) speed levers; 9) feed levers; 10) table movement levers; 11) foot stock ; 12) arbor yoke.

The spindle of the milling machine is driven by an electric motor through a train of gears mounted in the column.

The table of the plain milling machine may travel only at right angles to the spindle while the Universal Milling Machine is provided with a table that may be swiveled on the transverse slide for milling gear teeth, threads, etc.

Shaper and Planer

The machine tools of this group are generally used for machining flat surfaces, which is usually performed by a cutter that peels the chip from the work. The main motion is reciprocating and the feed is normal (perpendicular ) to the direction of the main motion.

The tool and the apron of a shaper are located on the ram. A chip is peeled off the work on the forward stroke . An adjustable table with "T"-slots holds work, vise , and other fixtures for holding the work.

The shaper has a rocker arm which drives the ram, and a mechanism for regulating the length of the stroke. The ram supports the tool head. The head carries the downfeed mechanism and will swivel from side to side to permit the cutting of angles. This is generally a hand feed, but some shapers are required with a power downfeed in addition to the regular hand downfeed.

The table of the shaper is of box form with "T"-slots on the top and sides for clamping the work. The cross rail is bolted directly to the frame or column of the shaper with bolts.

The automatic feed or power feed is obtained by a pawl which engages in a notched wheel or ratchet.

The main parts of the planer include the bed, the table that moves back and forth, the column, the crossrail which moves up and down on the column, and the tool heads that are fastened to the crossrail.

Grinding machines

A grinding machine is a machine which employs a grinding wheel for producing cylindrical , conical or plane surfaces accurately and economically and to the proper shape, size, and finish. The surplus stock is removed by feeding the work against the revolving wheel or by forcing the revolving wheel against the work.

There is a great variety of grinding machines. The machines that are generally used are cutter grinder,

surface grinder, centerless grinder, external grinder, internal grinder.

Principal parts of a plain grinding:

1. Base. The main casting of a plain grinding machine is a base that rests on the floor.

2. Tables. A sliding table, which is mounted on ways at the front and top of the base, may be moved longitudinally by hand or power to feed workpieces past the face of the grinding wheel.

3. Headstock and Tailstock. A motor-driven headstock and a tailstock are mounted on the left and right ends, respectively , of the swivel table for holding workpieces on centers. The headstock center on a grinder is a dead center, that is both centers are "dead" to insure concentricity of the periphery of ground work with its axis .

4. Wheel head. A wheel head that carries a grinding wheel and its driving motor is mounted on a slide at the top and rear of the base. The wheel head may be moved perpendicularly to the table ways, by hand or power, to feed the wheel to the work.

23. Pressing machine

The machine used for most cold-working operations is known as a press. It consists of a machines frame supporting a bed and a ram, a source of power, and a mechanism to cause the ram to move in line with and at right angles to the bed. The illustrations in this chapter show numerous typical designs of press equipment.

A press in itself is not sufficient as a production machine but must be equipped with tools commonly called dies and punches, designed for certain specific operations. Although some presses are better adapted for certain types of work than others, most of the forming, punching, and shearing operations can be performed on any standard press if the proper dies and punches are used. This versatility ? makes it possible to use the same press for many different jobs and operations, which is a desirable feature for short-run production.

Presses are capable of rapid production, since the actual time of operation is only the time necessary for one stroke of the ram plus the time necessary to feel the stock. Accordingly, production costs may be kept very low. Any product that can be fabricated from thin metal and does not require extreme accuracy in dimensional tolerances can be economically made on this type of machine. This special adaptability to mass-production manufacture of automotive and aircraft parts, hardware specialties, toys, and kitchen appliances .

24. Automatic Machine

Each machine tool discussed in previous chapters represents a basic cutting machine. Some particular cutting operation, such as turning, drilling, milling, or grinding, can be performed on each. They can be highly productive. Nevertheless each perform only a single function or at best a limited number of functions. Most parts require several different operations in their fabrication- one surface is rough machine, another superfinished , a hole drilled and a slot milled, all on the one part. Thus, the tool must be changed, the workpiece indexed and shifted from one machine to another. This results in much expenditure of labor and much nonproductive down-time.

One way of improving this situation is to design a machine tool on which more than one kind of cutting operation can be performed. Another is to enable the machine to perform its operations successively on the same workpiece without any intermediate handing. A third is automatic gaging of machine features with an arrangement for ejecting the finished part and inserting another blank . A final refinement is to incorporate feedback controls that regrind and even reset tools, or make other adjustments as directed automatically by gage reading.

Complete automation of a machine tool includes all the above. Thus, the machine is equipped not only to

perform its cutting automatically but also to "decide" what adjustments must be made to machine work according to specifications .

Broadly then, automatic machining comprises cutting where all tool and work-material movements are so actuated that duplicate parts may be made repeatedly without continuous attention. If cutting operations are automatic but an operator is needed to remove finished parts or reload or reset the machine, semi-automatic operation is generally said to exist. In either case, machine time is reduced and dimensional precision often improved.

25. Sources of Pressure-Pumps and Compressors

Fundamentally most pumps suitable for pumping hydraulic fluid will operate with air or gas, although most oil pumps make poor air compressors , and some compressors will not operate with incompressible fluid without modification.

从原理上讲，适于泵送流体的大多数泵都可以泵送空气或气体，尽管大多数油泵几乎不作为空气压缩机来用，而某些压缩机朱作调整则不可以输送非压缩性流体。

General considerations. The main requirements of a hydraulic pump capable of delivering sufficiently great a pressure to be of practical use are:

考虑原则。对一台可以传送足够大压力以供实际使用的液压泵能力的主要要求是:

a. Means for controlling fluid leakage either by special sealsi:l or close working clearances .

控制流体泄漏的措施。要么用特殊密封要么紧缩加工间隙。

b. A substantially uniform , non-pulsating delivery.

要真正均匀而非脉冲式输送。

c. The absence of trapping of fluid during rotation, since the fluid is for all practical purpose incompressible.

在运行中不存在空穴现象，因为作为实际用途的流体都是非压缩性的

d. Mechanical balance to a sufficient degree to enable the pump to be run as fast as possible, to reduce bulk for a given output.

机械平衡达到足够程度以使泵能尽可能快地旋转，目的是已定输出流量时减小泵的体积

e. Adequate provision for minimizing the effect of distortion of the working parts, casing , est., due to the internal pressure in the pump.

由于泵内有内压力，要有充分的措施，以最大限度减小工作零件、泵壳等的变形的影响

f. Low clearance volumes so that the pump will act momentarily during priming , or with aerated fluid, as a compressor, to discharge the air through the delivery line, instead of leaving it trapped in the pump.

间隙量要小，以便在起动期间很快动作，对含气流体，泵可像压缩机那样，把空气通过输送管线排出，而不让它沸留在泵中

g. Adequate inlet valve or port provision to enable the pump to create a good suction , or alternatively ?, as in the case of aircraft, to operate at high altitude , and with relatively thick fluids. It should be noted that the time of opening of the inlet valve or port is almost as important as the size of the port.

配置适当的进油阀或配流装置，以使泵能产生良好真空吸油作用，或者另一种情况下即飞机上高空。飞行操作的液压装置或较高粘度作为液压油时更应采取这些措施，应该注意的是入口阀或油门开启的时间，这几乎和油口尺寸一样重要。

The main requirements of a good compressor are:

一台良好压缩机的主要要求是

a. the smallest possible clearance volume compatible with mechanical clearance; this is because any gas compressed in the clearance will expand again instead of being discharged, and will thus adversely

affect not only the output of the pump, but the maximum pressure that can be achieved .

与机械间隙相适应的尽可能小的间隙容积。这是因为在间隙容积中被压缩的任何气体都将再次膨胀而不是被排放掉。相反，不仅将影响泵的输出，而且影响可能产生的最高压力

b. Except on low-pressure pumps, two or more stages of compression with as much intercooling between stages is possible. This is desirable , firstly, to reduce the wastage of work and output due to the gas being compressed adiabatically instead of isothermally , and, secondly, to reduce the overall loss of output due to clearance volume.

除低压泵外，要有两个或更多的压缩阶段。使阶段间有尽可能多的中间冷却。由于气体是进行绝热压缩的而不是等温过程压缩的，因此，首先希望减少功和输出量的损失。其次，由于间隙容积的原因，要减少总体上的输出损失。

c. Pre-compression of the air in the pump up to the pressure of the delivery line. Although the normal reciprocating pump with an automatic or spring-load delivery valve will ensure this, some of the rotary compressors have to be ported specially to obtain pre-compression, and with some it is not possible at all. Without pre-compression, as soon as the delivery port opens, the gas in the delivery pipe expands back into the pump, and the whole volume has again to be compresse

d. A rotary compressor with pre-compression cannot be operated with hydraulic fluid.

泵中空气预压缩压力升高到输送管线中压力。尽管标准往复泵因具有自动阀或受压弹簧阀能保证这点，但某些旋转式压缩机则必须专门配上气阀来配流，以便获得预压缩，而另一些泵则全然不可能做到。泵内无预压力，一旦输气阀口打开，管线中气体膨胀而回到泵内，泵内全部流体不得不再次被压缩。具有预压缩装置的旋转压缩机不可能输送油流。

d. Provision for air or water cooling of the cylinder so that the temperature of the air in the compressor may be kept as near isothermal as possible, and the volume of air being delivered correspondingly increased. This is a feature not normally necessary on a hydraulic pump.

缸体气冷或水冷措施，使得压缩机中气体温度尽可能保持等温状态，而被输送的气体体积相应增加。这是掖压泵在正常情况下所不需要的特性。

e. Means for controlling gas leakages during compression either by piston rings on a reciprocating piston compressor, or fine clearances on the rotary types.

在压缩期间，控制气体泄漏的措施是靠压缩机往复运动活塞上的密封环或者依靠旋转式压缩机上的细微间隙。

f. Adequate inlet valve area to prevent throttling of the incoming air, with the consequent loss of volumetric efficiency.

配置足够的进气阀的面积以防止因进来的气体在节流过程中所产生的容积效率的损失。

The main types of pump and compressor use pistons, meshing gears or rotating vanes, these having been found to give good high pressure performance . Other types of pumps, such as centrifugal pumps or turbo-compressors, are not used for pressure systems as they do not produce high enough pressure to be useful.

各种主要类型的泵和压缩机都使用活塞、相啮合的齿轮或旋转叶轮，这些类型的泵和压缩机已经证明能提供高压和良好性能。其他类型的泵，例如离心泵、涡轮压缩机，是不用于压力系统的，因为它们不能产生有用的足够高的压力。

26. Variable Speed Hydraulic Systems

It is particularly important on many hydraulic systems, as on machine tools, to be able to vary the speed of operation at will. This can be carried out in the following ways, sometimes more than one way being combined

许多液压装置，如像机床上用的，其操作速度能随意变化，那显得特别重要。这种变速可以以下列方法，有时以一个以上的方法相结合来实现。

a. By varying the pump output manually;

用千动控制改变泵的输出;

b. By using several pumps in combinations ;

利用几台泵组合

c. By restrictingris5trikt or throttling the output of an automatically variable delivery pump, or a pump accumulator system, or by throttling the inlets;

靠自动节流调节输送泵的输出量，或靠泵的蓄压器装置，抑或借助入口节流调节

d. By by-passing part of the pump output with a flow dividing valve;

通过泵的旁路，经分流阀输出

e. By varying the volume of the operating jack .

操纵动力油缸改变流量

1. Variation in Pump Delivery. Pump delivery can be varied by-

泵送量的变化。泵的输送量可以靠以下方法变化

a. Alteration in its speed;

其速度改变

b. Alteration of its stroke in a variable stroke type of pump;

在可变冲程泵中，改变其冲程

c. Using two or more pumps of different delivery in parallel so that stopping and starting the pumps in various combinations different total deliveries can obtaine

d.

利用两台或更多的泵并联送出不同的榆送量。因此借助不同的组合来启、停这些泵，可以获得不同输出总量。

The first system is an easy one when the pump is electrically driven, although the electric motor involved is comparatively complicated for normal requirements. Mechanical variable speed gear boxes have been used successfully with constant speed electric drive.

当泵是用电力驱动时，第一种装置是一种容易实现的装置。虽然为了实现标准要求，包括电机在内的系统是比较复杂的。机械变速齿轮箱已经成功地用于恒速的电力驱动

Several of the pump mechanisms previously described can readily be adapted to give a varying output by reducing the working stroke manually by means of a control wheel, etc.

如前所述，泵的几种机构借助手动控制轮、通过减少工作冲程，很容易被采用来提供可变的输出The third system is simple enough, but varies the output in fixed steps. Two pumps in parallel can give three ranges of output corresponding to Pump A, Pump B, Pump A plus B.

第三种装置是够简单的了，但其是以确定步骤来改变输出的。并联设置的两台泵可提供相当于下列的三种范围的输出

Three pumps in parallel can give seven steps corresponding to-

Pump A, Pump A plus B, Pump B plus C.

Pump B, Pump A plus C, Pump A plus B plus C.

Pump C.

并联设置的三台泵可提供相当于下列的七种的输出

Since, however, variable stroke pumps are readily available , such a complication as three pumps in parallel hardly seems worthwhile although the two-pump system is probably excellent for such duties as presses, etc., where a great part of the working stroke is at low pressure, where a relatively cheap type of pump can be used, cutting out in favor of a smaller delivery high pressure pump for the final working stroke. Automatic isolation of the low pressure pump can be effected by a valve. Any normal type of automatic cut-out will operate in the low-pressure system to by-pass it, without interference from the other pump.

因而，可变冲程泵是容易见效的，像这样三个泵并联几乎肯定是合算的，尽管两泵装置对于像在压

英语翻译答案

第一单元 1.They took advantage of our helpless situation and took over our company. 2.Although there are still difficulties ahead of us. I am sure that we Chinese people will have the wisdom to bring about the peaceful unification of our country on our own. 3.It is wrong to emphasize nothing but GDP. It will give rise to many serious problems. 4.He loves to show off his wealth, but that is all in vain. People still avoid him as though he were poison. 5 He soon fell in love with the village and decided to make it a beautiful garden together with other villagers 6.We must spend more money in fighting against global warming. Besides, we must resort to tough laws. It is not just a matter of money. 7.When the police reached the school, the students and teachers were still in a daze. 8.This corrupt official was still clinging to his power. He refused to step aside. 9.When the man finally came into view, I found it was my father. I didn’t know how he managed to find this place in the heavy snow. At that moment, I burst into tears.

英语课后翻译答案新

U n i t1 1. 任何年满18岁的人都有资格投票。(be eligible to, vote) Anyone over the age of 18 is eligible to vote. 2. 每学期开学前，这些奖学金的申请表格就会由学校发给每一个学生。(apply for, scholarship) A form to apply for these scholarships is sent by the university to every student before the start of every semester. 3. 遵照医生的建议，我决定戒烟。(on the advice of) On the advice of my doctor, I decided to give up smoking. 4. 公园位于县城的正中央。(be located in) The park is located right in the center of town. 5. 这所大学提供了我们所需的所有材料和设备。(facilities) The university provides all the materials and facilities we desire. 1. 他们花了多年的时间寻找内心的平静，但是收效甚微。(search for) They spent many years searching for peace of mind, but with little success. 2. 这种新药的成功研制已经使许多疾病的治疗发生了根本性的变革。

郭著章 李庆生《英汉互译实用教程》笔记和课后习题(含考研真题)详解(大写、标点符号与英汉互译)

第10章大写、标点符号与英汉互译 10.1 复习笔记 第1节大写与翻译 一、英文大写的最常用规则 1. 历史上的事件、时期和文件。如：美国的“南北战争”为“Civil War”。 2. 商品的牌子名称。如：飞鸽牌自行车Flying—Pigeon bicycle，可口可乐Coca Cola。 3. 星期名、月份、假日。如：星期一Monday，三月March，国庆日National Day。 4. 人名和地名，即数量最多的专有名词。如：邓小平Deng Xiaoping，莎士比亚Shakespeare，伦敦London。 5. 标题与书名等专名中的实词与两个音节及其以上的虚词。如：《为人民服务》“Serve the People”，《双城记》A Tale of Two Cities，《无事生非》Much Ado About Nothing。 6. 圣经中关于上帝的名词与代词。如：God，Lord，Christ，Jesus，He，Him，Himself 和His。 7. 职称、头衔和亲属关系称呼用在人名前头时。如：王力教授Professor Wang Li，史密斯博士Dr. Smith。 8. 机关、学校、建筑物和商业机构的名称。如：教育部Education Ministry，武汉大学Wuhan University，人民大会堂the Great Hall of the People。 9. 种族、国籍、语言和宗教方面的词语。如：黑人Black People或Negro，意大利

人Italian，中国籍(中国人或中国人的)Chinese，汉语Chinese天主教Catholic，新教徒Protestant。 10. 其他一切有特殊含义的词语，包括一句或一信的开头词、诗行的开头词、直接引语的开头词、强调词语等，和前9条中所说的词语一样，其首字母或全部字母必须大写。如： (1) 他爱国。 He loves his motherland. (2) 亲爱的先生： Dear Sir， (3) (诗句)听!那山谷深深，/充满了她歌唱的清音。 O listen! for the vale profound/Is overflowing with the sound. 第2节汉译英与标点 一、汉语标点符号 汉语书面语中共有l6种标点符号，它们是：l. 句号(。)2. 问号(?)3. 叹号(!)4. 逗号(，)5. 顿号(、)6. 分号(；)7. 冒号(：)8. 引号(“”)9. 括号(( ))10. 破折号(—)11. 省略号( (12) 着重号(. )13. 连接号(-)14. 间隔号(·)15. 书名号(《》)16. 专名号(____) 要正确地使用标点符号，记清它们的位置亦非常重要。《标点符号用法》对每种符号的位置也作了明确规定：“句号、问号、叹号、逗号、顿号、分号和冒号都是占一个字的位置，通常不出现在一行之首。引号、括号、书名号的前一半不出现在一行之末，后一半不出现在一行之首。破折号和省略号都占两个字的位置，中间不能断开。连接号和间隔号一般占一个字的位置。在书写和印刷时，这四种符号上下居中。着重号、专名号和浪线式书名号标在字

英语翻译题目和答案

汉译英专项练习 一、倍数增减的表示法 5 1) Force N1 _______________(比力N2大2.5倍). is 2.5 times greater than Force N2 （考点：倍数+形容词/副词比较级+ than） 2) This substance _______________(反应速度是另外那种物质的三倍). reacts three times as fast as the other one （考点：倍数+ as +形容词/副词+ as） 3) The earth _______________(是月球大小的49倍). is 49 times the size of the moon （考点：倍数+名词） 4) The landlord _______________(想将租金提高三分之一). wants to raise the rent by a third （考点：动词+ by +数词/百分比/倍数） 5) They _______________(计划将投资增加一倍). plan to double their investment （考点：double +名词） 二、时态6 1) Be quick, _______________(否则等我们到达教堂时婚礼就已经结束了). or the wedding will have finished by the time we get to the church （考点：将来完成时） 2) When she got home, _______________(孩子们已经睡着了). the children had fallen asleep （考点：过去完成时） 3) When I prepare for the college entrance examination, _______________(我姐姐将在海边度假). my sister will be taking her vacation at the seaside （考点：将来进行时） 4) I_______________(一上午都在修改我的简历). have been revising my resume all the morning （考点：现在完成进行时） 5) Do you often go on holiday? _______________(不，我已经有五年没有度假了). No. It has been five years since I went on holiday （考点：It has been…since sb. did sth.表示某人有多长时间没有做某事了） 6) He joined the army in October, 2001. _______________(他参军已五年了). He has been in the army for 5 years （考点：1.现在完成时；2.要用持续性动词才能接一段时间） 三、被动语态5 1) The blackboard and chalk _______________(正在被电脑和投影机所取代). is being replaced by the computer and the projector （考点：被动语态的现在进行时） 2) The book _______________(到今年年底就将已出版). will have been published by the end of this year （考点：被动语态的将来完成时）

新视野大学英语课后习题翻译答案

新视野大学英语（第二版）读写教程2 1至7单元课后翻译答 案总结 IA：她连水都不愿意喝一口，更别提留下来吃饭了。 She wouldn’t take a drink , much less would she stay for dinner. 他认为我在对他说谎，但实际上我讲的是实话。 He thought I was lying to him , whereas I was telling the truth. 这个星期你每天都迟到，对此你怎样解释 How do you account for the fact you have been late every day this week 他们利润增长的部分原因是采用了新的市场策略。 The increase in their profits is due to their new market strategy. 这样的措施很可能会带来工作效率得提高。 Such measures are likely to result in the improvement of work efficiency. 我们已经在这个项目上投入了大量时间和精力，所以我们只能继续。 We have already poured a lot of time and energy into the project , so we have to carry on. IIA: 尽管她是家里的独生女，他父母也从不溺爱她。 Despite the fact that she is the only child in the family , her parents never baby her .

(完整版)医学专业英语翻译及答案

Chapter 1 Passage 1 Human Body In this passage you will learn: 1. Classification of organ systems 2. Structure and function of each organ system 3. Associated medical terms To understand the human body it is necessary to understand how its parts are put together and how they function. The study of the body's structure is called anatomy; the study of the body's function is known as physiology. Other studies of human body include biology, cytology, embryology, histology, endocrinology, hematology, immunology, psychology etc. 了解人体各部分的组成及其功能，对于认识人体是必需的。研究人体结构的科学叫解剖学；研究人体功能的科学叫生理学。其他研究人体的科学包括生物学、细胞学、胚胎学、组织学、内分泌学、血液学、遗传学、免疫学、心理学等等。 Anatomists find it useful to divide the human body into ten systems, that is, the skeletal system, the muscular system, the circulatory system, the respiratory system, the digestive system, the urinary system, the endocrine system, the nervous system, the reproductive system and the skin. The principal parts of each of these systems are described in this article. 解剖学家发现把整个人体分成骨骼、肌肉、循环、呼吸、消化、泌尿、内分泌、神经、生殖系统以及感觉器官的做法是很有帮助的。本文描绘并阐述了各系统的主要部分。 The skeletal system is made of bones, joints between bones, and cartilage. Its function is to provide support and protection for the soft tissues and the organs of the body and to provide points of attachment for the muscles that move the body. There are 206 bones in the human skeleton. They have various shapes - long, short, cube - shaped, flat, and irregular. Many of the long bones have an interior space that is filled with bone marrow, where blood cells are made. 骨骼系统由骨、关节以及软骨组成。它对软组织及人体器官起到支持和保护作用，并牵动骨胳肌，引起各种运动。人体有206根骨头。骨形态不一，有长的、短、立方的、扁的及不规则的。许多长骨里有一个内层间隙，里面充填着骨髓，这即是血细胞的制造场所。 A joint is where bones are joined together. The connection can be so close that no movement is possible, as is the case in the skull. Other kinds of joints permit movement: either back and forth in one plane - as with the hinge joint of the elbow - or movement around a single axis - as with the pivot joint that permits the head to rotate. A wide range of movement is possible when the ball - shaped end of one bone fits into a socket at the end of another bone, as they do in the shoulder and hip joints. 关节把骨与骨连接起来。颅骨不能运动，是由于骨与骨之间的连接太紧密。但其它的关节可允许活动，如一个平面上的前后屈伸运动，如肘关节；或是绕轴心旋转运动，如枢轴点允许头部转动。如果一根骨的球形末端插入另一根骨的臼槽里，大辐度的运动（如肩关节、髋关节）即成为可能。 Cartilage is a more flexible material than bone. It serves as a protective, cushioning layer where bones come together. It also connects the ribs to the breastbone and provides a structural base for the nose and the external ear. An infant's skeleton is made of cartilage that is gradually replaced by bone as the infant grows into an adult. 软骨是一种比一般骨更具韧性的物质。它是骨连结的保护、缓冲层。它把肋骨与胸骨连结起来，也是鼻腔与内耳的结构基础。一个婴儿的骨骼就是由软骨组成，然后不断生长、

英汉互译教程要略

英汉互译教程要略 1．Joint military exercises have increased in the region, to the detriment of trust between countries. 联合军事演习在本地区有增无减，不利于国家间建立信任。 2．This old man gets up and goes to bed with the sun everyday. 这位老翁每天黎明即起，日落而息。 3．A nearby object falling into a black hole is never heard of again. 附近的天体一旦落入黑洞，就会销声匿迹。 4．我们应该抢时间赶任务。 We should work against the clock. 5.These hospital expenses made inroads on my savings. 这些住院费耗掉了我大部分积蓄。 6．They killed a bottle of Kaoliang between them. 他们二人对酌，把一瓶高粱酒喝得一干二净。 7．When it came to reading, they were as good as blind. 一拿起书本，他们可都成了睁眼瞎了。 8．Blood is thicker than water. 血浓于水。 9．人们笑贫不笑娼。 People ridicule poverty but not prostitutes. 10. Last night I heard him driving his pigs to market. 昨夜我听见他鼾声如雷。 11．They ran away as fast as their legs could carry them. 他们拼着命地逃跑。 12．People were born survivors. 人的生存能力是与生俱来的。 13．这个环境工程是个“民心工程”。 The environment-friendly project is a “popularity-winning” project. 14. 语言这东西不是随便可以学好的，非下苦功夫不可。 The mastery of a language is not easy and requires painstaking effort. 15. 会议开得冷冷清清，有时甚至开不下去了。 The meetings were marked by such absence of living discussions that at times they were almost on the point of breaking up. 16. They pay lip-service to education but don’t work for better schools. 他们口惠而实不至，口口声声支持教育，却又不肯为改善学校条件做一些实际工作。17．Unemployment has stubbornly refused to contract for more than a decade. 失业人数高居不下，已经十多个年头了。 18．有些厕所似乎仍是这次卫生大扫除活动的死角。 Some toilets seem immune to the clean-up campaign. 19. 这个摊贩叫卖道：“快来买呀，过了这村可没这个店啦。” The street peddler hawked, “Now or never!” 20. Why carry coals to Newcastle? 何必多此一举？ 21．You’re just teaching your grandmother how to suck eggs. 你这是在班门弄斧。 22．His being neglected by the host added to his uneasiness.

英语翻译答案

汉译英 1.广场舞是社区中老年居民以健身、社交等为目的在广场、公园等开敞的地方进行的健身操或舞蹈，通常以高分贝的音乐伴奏。广场舞在中国大陆无论南北皆十分普遍。对于广场舞的确切认识，社会学界及体育界目前均未达成共识。广场舞的高分贝音乐常常造成噪音滋扰，因此许多居民反对在小区中跳广场舞。 The square dancing is a bodybuilding exercise or dance performed in wide and open places such as squares and parks among the middle-aged and old residents in communities, with the purpose of bodybuilding, socializing and so on, generally accompanied with high-pitched music. The square dancing is very popular all over mainland China, whether in the north or in the south. Neither the sociological circle nor the sports circle has currently reached a consensus on the exact perception of the square dancing. The high-pitched music of the square dancing often causes noisy disruption, and therefore many residents are opposed to the square dancing in communities. 2.故宫，又称紫禁城，是明、清两代的皇宫，二十四位皇帝在此生活起居和处理政务。它是世界现存最大、最完整的木质结构的古建筑群(architectural complex)。宫殿墙壁的色调以红色和黄色为主,红色代表快乐、好运和财富，而黄色代表帝王的神圣和尊贵。近十几年来，故宫平均每年接待中外游客600-800万人次，随着旅游业的繁荣，游客人数有增无减，可见人们对故宫的兴趣长盛不衰。 The Imperial Palace, also known as the Forbidden City, was the palace in Ming and Qing Dynasties where 24 emperors lived and handled government affairs. It is the largest and most complete existing ancient wooden architectural complex in the world. The palace wall was painted mainly in red and yellow. Red represents happiness, luck and fortune while yellow symbolizes imperial holiness and dignity. In recent decades, the Imperial Palace is visited annually by six to eight million tourists at home and abroad. Moreover, with flourishing tourism industry, the number of tourists keeps increasing. It shows people’s everlasting and unfading interest in the Imperial Palace. 3.《新闻联播》是中国中央电视台（CCTV）每日播出的一个新闻节目。节目每次播出时长一般为30分钟。它被中国大陆大多数地方频道同时转播，这使得它成为世界上收看人数最多的节目之一。自从1978年1月1日首次播出以来，它就以客观、生动、丰富的纪实手段记录着中华大地每一天的变化。作为中国官方新闻资讯类节目，《新闻联播》以沉稳、庄重的风格著称。 Xinwen Lianbo is a news program broadcast by China Central Television (CCTV) every day. It generally takes 30 minutes every time to broadcast the program. It is relayed simultaneously by most local television channels in the mainland of China, which makes it one of the world’s most-watched programs. Since it was first broadcast on January 1st, 1978, it has been recording the changes of every day throughout China by documentary means that is objective, vivid and rich. As the Chinese official news information program, Xinwen Lianbo is well-known for its

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Unit 1 From her accent I guess she’s from the Northeast. 从她的口音我猜她是来自东北地区的。 It was very clever of her to turn his argument against himself. 她很聪明，使他对自己的论点 I found a couple of shoes under the bed but they don’t make a pair. 我在床下发现了一双鞋，但他们不做一双 4. Dr. Bright always takes his time as he examines his patients and treats them with extreme care. Bright博士总是把他的时间用于他检查他的病人，并把他们的极端护理 5. British companies are trying to avoid the fate their American counterparts have already suffered. 英国公司正试图避免他们的美国同行已经遭受的命运。 6. Wilfred’s remarks confirmed me in my opinion that he was an honorable young man. 威尔弗雷德的话证实了我在我看来，他是一个光荣的年轻人 7. The key witness for the prosecution was offered police protection after she received death threats. 检察机关的主要证人在收到死亡威胁后提供了警方的保护 8. I thought that was the end of the matter but subsequent events proved me wrong. 我认为这是事情的结束，但随后的事件证明我错了。 9. Having practiced for so long, the New York baseball team stands a chance winning the World Series this year. 经过这么长时间的练习，纽约棒球队赢得了今年的世界系列赛的机会。 10. At the trial , Bob’s teacher, who was called as a character witness, said he was a quiet boy who had never been in trouble before. 在审讯中，鲍伯的老师，被称为证人，说他是个安静的男孩以前从未惹过麻烦。 Unit 2 11. We’ve just had a very fruitful meeting with the management and we’re now much more hopeful about the pay rise. 我们刚刚与管理层有了一个非常富有成效的会议，我们现在对加薪的希望更大了 12. The book I’m reading explains the evolution of plant and animal life on earth. 我读的这本书解释了地球上动植物的进化

英汉互译一第1课教案

广西师范学院《英汉互译（一）》课程教案 编号: 15-1 开课单位：外语系授课教研室：翻译写作 课程名称：《英汉互译（一）》授课教师：唐旭光 教材：《新编英汉互译教程》，授课对象：06级英语专业2、3、5班

《英汉互译（一）》第一讲翻译简论与主要翻译方法 （A Brief Discussion of Translation and Major Translation Approaches） 1. Introduction Translation studies started along with translation practice. Translation theories developed flourishingly in the 20th century, especially in the second half of the last century. In fact, translation, which is a very complex phenomenon, is related to different disciplines, such as linguistics, psychology, sociology, cultural anthropology, communication theory, literary criticism, aesthetics, and semiotics. As translation study is a cross-discipline and cross-culture subject involving many aspects of human knowledge, the lack of a fully acceptable theory of translation should not come as a surprise. Meanwhile, quite a number of translation approaches and strategies have become universally acceptable and widely applicable. They are, of course, the fruits of many translation theorists and translation practitioners at home and abroad. 2.The Origin of Translation Language makes it possible for people to communicate with one another freely so as to complete important tasks in human life. Translation makes it possible for people from different languages to communicate with one another so as to complete important tasks in their life. Theodore Savory points out, “Translation is almost as old as original authorship and has a history as honorable and as complex as that of any other branch of literature”(申雨平, 2002:4). In Zhou Dynasty there were different forms of address for translators in different places. “Translators are called Ji in the east, Xiang in the south, Didi in the west, and

郭著章《英汉互译实用教程》(第4版)教材配套题库-第5章 翻译常用的八种技巧【圣才出品】

第5章翻译常用的八种技巧 5.1 重译法 一、英译汉 1. It may seem strange to put into the same packet an industrial revolution and two political revolutions. But the fact is that they were all social revolutions. 【译文】把一场工业革命同两次政治革命归作一类似乎有点奇怪，但事实上这三次革命都是社会革命。 2. Two things are outstanding in the creation of the English system of canals, and they characterise all the Industrial Revolution. 【译文】在修建英国的运河网的过程中，有两点是非常突出的，而这两点也正是整个工业革命的特点。 3. The canals were arteries of communication: they were not made to carry pleasure boats, but barges. 【译文】运河是交通的动脉，开运河不是为了走游艇，而是为了通行驳船。 4. James Brindley was a pioneer in the art of building canals or, as it was then called, ‘navigation’. 【译文】布林德雷是开凿运河的先驱者，当时人们把开凿运河叫做navigation。

5. Several factors accounted for this extraordinary achievement. One was the expansion into the west. Another was the application of machinery to farming. 【译文】取得这一特殊成就有几方面的原因：第一个原因是向西部的扩展，第二个原因是机器在农业上的应用。 6. …for the establishment of agricultural and industrial colleges. These were to serve both as educational institutions and as centers for research in scientific farming. 【译文】……以便建立农业和工业学院。这些学校一方面是教育机关，另一方面，也是农业科学的研究中心。 7. …This is nothing li ke back home in Colorado. We have rains there, too. Thunderstorms in spring and summer... 【译文】……这跟家乡科罗拉多的情况迥然不同。科罗拉多也下雨。春夏两季雷雨交加……【解析】原文第二句用there代替in Colorado，而译文重复“科罗拉多”。 8. The world watches. The world listens. The world waits to see what we will do. 【译文】全世界在注视着。全世界在倾听着。全世界在等待着看我们将做些什么。 9. As you said in your toast, the Chinese people are a great people, the American people are a great people.

英语翻译答案

Unit 1 3. 战斗结束后, 双方均宣称获胜。 After the battle both sides claimed victory. 她对这块土地产权提出的要求最终得到法庭的认可。 Her claim to the ownership of the land was finally recognized by the court. 4. 我从没有感到忌妒。 There has never been any jealousy on my part. 6. 他最近出的书中提到了中东问题。 His recent book makes references to the issue of the Mideast. 7. CF: efficient & effective 8. 我们听到邻居正在争吵。We could hear the neighbors arguing. 9. 每一个人都有永远不可剥夺的权利。 Every individual has rights which must never be taken away. 10. 他是个个性很强的有抱负的人。 He was an ambitious man with a strong personality. 费德勒是网球界最著名的人物之一。 Roger Federer is one of the best-known personalities in the world of tennis. CF: personality, character, nature & temper 11. 想必你要在吃饭前打开行李休息一下。 No doubt you’ll want to unpack and have a rest before d inner. 12. 他们的资金在一定程度上来自广告收入。 They are financed to a certain extent by advertising revenue. 14. 他们往往持极端观点。 They often go to extremes in their views. 15. 我假定他说的是真的。 I assumed his story to be true. CF: assume, presume & suppose 16. 就在我昏倒之时，他一把拉住了我。 He caught me at the precise moment that I fainted. 17. 美国的国会大致相当于英国的议会。 The US Congress is roughly equivalent to the British Parliament. 18. 男孩也许会拒绝与女孩一起玩，女孩也一样。 The boys may refuse to play with the girls, and vice versa. 19. 这本小册子提供了当地各类服务的有用信息。 This booklet provides useful information about local services. 旅馆为客人们提供擦鞋服务。 The hotel provides a shoe-cleaning service for guests. 21. 这个电影是以马克?吐温的小说为题材的。 The film is based on a novel by Mark Twain. CF: base, basis & foundation 22. CF: continual, continuous, successive & constant 23. 没有办法查明发生了什么。There is no means of finding out what happened.